The present invention relates to a disk drive device and is, in particular, suitable for a disk drive device that is mounted on a portable apparatus and an information apparatus for vehicles.
In environments of use of portable apparatuses and information apparatuses for vehicles, in general, temperature and humidity change in a wide range compared with those used in offices, computer rooms, and the like and often involve rapid changes. In disk drive devices exposed to such environments, temperature in a housing, in which a disk is housed, changes rapidly and significantly to affect reliability of the apparatuses significantly. In a high-humidity environment, a head and a disk may attract each other to be damaged because of partial moisture condensation. In addition, corrosion of a magnetic metal layer may progress on a head surface and a disk surface. Consequently, recording and reproducing functions deteriorate. On the other hand, under low humidity, a lubricating function of a lubricant coated on the disk surface falls and wear of the head and the disk progresses. Therefore, in order to secure reliability of the disk drive devices, it is important to keep humidity in the housing as constant as possible in an appropriate range.
As humidity control in conventional disk drive devices, for example, moisture absorbing members such as silica gel, activated carbon, and a moisture absorbing film are set in housings. A main object of these moisture absorbing members is to decrease humidity. A control method of increasing humidity in the case of low humidity is not taken into account. In addition, moisture absorbing abilities of these moisture absorbing members substantially depend on volumes thereof. Thus, in order to cope with severe environments, it is necessary to increase sizes of the moisture absorbing members. This is an obstacle to a reduction in size and a reduction in cost of the disk drive devices.
Thus, the magnetic disk device described in JP-A-2-1004 (patent document 1) has been devised. This magnetic disk device of the patent document 1 is mounted with a humidity control element having a hydrogen ion conductor and makes reversible humidity control possible according to voltage control. The magnetic disk device also makes it possible to control speed of a dehumidification amount and a humidification amount according to an applied voltage value. This humidity control element includes a hydrogen ion conductor consisting of a solid electrolyte and a pair of electrodes sandwiching this hydrogen ion conductor. The humidity control element communicatively connects one of the electrodes to the outside of a housing (a container) and communicatively connects the other electrode to the inside of the housing. By changing a direction of a DC voltage applied to the electrodes, it is possible to switch dehumidification and humidification in the housing by the hydrogen ion conductor.
This patent document 1 discloses a control method of performing operation of the humidity control element after detecting a start instruction or a stop instruction for a motor and a control method of performing operation of the humidity control element after detecting humidity in the housing with a humidity sensor.